VILLAGE of FRANKFORT 432 W. NEBRASKA STREET
FRANKFORT, IL 60423 815/469-2177
STORMWATER BASIN DESIGN GUIDELINES
ABSTRACT: In 2002, the Village of Frankfort adopted engineering design standards (Ordinance No. 1945) which established design criteria for stormwater management. The Village included provisions for the utilization of Best Management Practices (BMP) for the design of stormwater management systems. The primary objective of BMP are to improve water quality, utilize natural features on-site, and have no adverse impact to existing water resources. The Village has a preference for wet bottom and wetland designs for detention facilities over dry bottom. The enclosed guidelines are an enhancement to the Village Design Standards. They should be used as an additional tool to aid the developer in designing stormwater management facilities that are functional, maintainable and aesthetically pleasing. HOW TO USE: Once the volume of required stormwater detention and release rates have been calculated, the designer should layout the stormwater basin based on the enclosed criteria. Two (2) matrix sheets are provided which aid in the selection of the basin type and landscape options. In addition, photographs are included which depict final landscape appearance, water quality enhancement features and plant materials. Example cross sections for each respective basin type are also included. Village staff and our support personnel stand ready to assist the development community throughout the design process. The purpose of the guidelines is to advance creativity of design and promote quality development. February 10, 2004
Village of Frankfort Stormwater Basin Design Guidelines Page 2 Village of Frankfort Stormwater Basin Design Guidelines The following criteria are proposed as conservative standards for design of stormwater basins within the Village of Frankfort. If a developer wishes to exceed the standards, they (via their landscape contractor/designer) bear the burden of proof that the landscape material will be successful. Any deviation from village standards is subject to approval by the Village of Frankfort. The limits of acceptable fluctuation and drawdown times are based on best professional judgment for landscape treatments typical to wet and dry stormwater basin designs. I. Wet Basin Design
A. Wet Bottom Pond Minimum Area: 1.0 acre at NWL
Maximum Area: No maximum Depth: Over 25 percent of the bottom area at least 10.0 ft. deep Maximum Bounce: 100-year: 5.0 ft.
2-year: 1.0 ft. Maximum Drawdown Time: 100-year: above NWL by 0.5 ft. for ≤ 72 hrs
2-yr: above NWL by 0.5 ft. for ≤ 36 hrs
Maximum Slopes: Freeboard elevation to 2-yr water level: 4:1 2-yr water level to NWL: 8:1 NWL to 1.5 ft. below NWL: 20:1 (safety shelf) >1.5 ft. below NWL: 2:1 Freeboard to 1.5 ft. below NWL: 5:1 avg. max. Safety Shelf: 0.5 to 1.5 ft. inundation at NWL, 10.0 ft. avg. width (variable 8.0
to 12.0 ft.), with 25 percent of the shoreline 2.0 ft. shorter than maximum width
Shoreline Protection: Natural vegetation (preferred); armoring (conditioned upon
Village review and approval); biotechnical stabilization (depending on site-specific conditions); erosion control measures
Water Quality Enhancements: Maximize distance between inlets and outlets; no low-flow
channel to be provided; energy dissipation measures at outlets; measures such as aerators, cascading streams, water falls, etc. are recommended for aesthetic appeal and to promote water circulation and aeration
Village of Frankfort Stormwater Basin Design Guidelines Page 3
Landscape Options: Natural, ornamental hybrid, low maintenance turf, and turfgrass (depending on site conditions and adjacent/adjoining land uses); public access via stone outcroppings, groomed areas, etc. are recommended
B. Wetland Bottom Minimum Area: 8,000 s.f. at NWL
Maximum Area: No maximum Depth: ranging from 0.5 to 5.0 ft. (average 3.0 ft.); at least 5 percent of
the area below NWL having pockets up to 5.0 ft. deep
Maximum Bounce: 100-year: 5.0 ft. 2-year: 1.0 ft.
Maximum Drawdown Time: 100-year: above NWL by 0.5 ft. for ≤ 72 hrs
2-yr: above NWL by 0.5 ft. for ≤ 36 hours
Maximum Slopes: Freeboard elevation to 2-yr water level: 4:1 2-yr water level to 0.5 ft. below NWL: 8:1 0.5 to 1.5 ft. below NWL: variable 8:1 to 12:1 (safety ledge) >1.5 ft. below NWL: 2:1
Freeboard to 1.5 ft. below NWL: 5:1 avg. max. Shoreline Protection: Natural vegetation; biotechnical stabilization (depending on site-
specific conditions); erosion control measures Water Quality Enhancements: Maximize distance between inlets and outlets; no low-flow
channel to be provided; energy dissipation measures at outlets; measures such as aerators, cascading streams, water falls, etc. are strongly recommended to maintain cooler water temperatures, promote water circulation and aeration, and provide aesthetic appeal
Landscape Options: Natural, ornamental hybrid, and low maintenance turf; public
access via stone outcroppings, groomed areas, etc. are recommended
Village of Frankfort Stormwater Basin Design Guidelines Page 4 II. Dry Basin Design
Minimum Area: No minimum Maximum Area: 8,000 s.f., unless approved by the Administrator Safety Shelf: Not applicable
Maximum Bounce: 4.0 ft. Maximum Drawdown Time: No more than 20 percent of the basin with standing water for
more than 72 hours for 100-year storm event
Maximum Slopes: 4:1
Water Quality Enhancements: Promote sheet flow; no low-flow channel to be provided; maximize distance between inlets and outlets; energy dissipation measures at outlets
Landscape Options: Naturalized, turfgrass, ornamental hybrid, and low maintenance
turf Last Revised: 30 January 2004 \\planres1\F\LandArch\P20161-00 Frankfort Review\Guidelines\Tasks 1- 3 Final Draft.doc
Village of Frankfort Stormwater Basin Design Guidelines Page 5
Basin Type
Parameter
Wet
Bot
tom
Wet
land
B
otto
m
Dry
Bot
tom
Associated Land Use Natural Area Park
Residential
Commercial Adjacent Land Use Natural Area Park Residential
Commercial
Right-of-Way Basin Size < 8,000 s.f. with no NWL
≥ 8,000 s.f. at NWL ≥ 1.0 ac. at NWL Drawdown Time Rapid
Moderate
Slow Level of Fluctuation Low
Moderate
Extreme Compatible
Compatible, with limitations
V
illag
e of
Fra
nkfo
rt
St
orm
wat
er B
asin
Lan
dsca
pe O
ptio
ns M
atri
x
Wet
Bot
tom
W
etla
nd B
otto
m
Dry
Bot
tom
Lan
dsca
pe T
ypes
Freeboard to 10-yr WL
10-yr WL to 2-yr WL
2-yr WL to NWL
NWL to 0.5' below NWL
Safety shelf (-0.5' to 1.5' below NWL)
Freeboard to 10-yr WL
10-yr WL to 2-yr WL
2-yr WL to NWL
NWL to 0.5' below NWL
More than 0.5' below NWL
N
atur
al
Lo
w-p
rofil
e Pr
airie
M
esic
Pra
irie
W
et-M
esic
Pra
irie
Sh
orel
ine
Emer
gent
D
eepw
ater
Em
erge
nt
(opt
iona
l)
O
rnam
enta
l Hyb
rid
L
ow M
aint
enan
ce T
urf
T
urfg
rass
Com
patib
le
C
ompa
tible
, with
lim
itatio
ns
Village of Frankfort Stormwater Basin Design Guidelines Page 11
Photo 1 – Wet bottom basin with broad emergent shelf and wet-mesic prairie slopes with clusters of woody vegetation. Note the irregular shape of the basin. (early summer)
Photo 2 – Wetland bottom basin with emergent vegetation, minimal open water, and mesic prairie slopes (summer)
Village of Frankfort Stormwater Basin Design Guidelines Page 12
Ps
Photo 3 – Wet bottom basin with water quality aeration system, a broad emergent zone, and adeepwater emergent zone. Note that a portion of the shallow basin slope is vegetated with traditional turfgrass (summer) [Photo courtesy of EnCAP, Inc.]
hoto 4 – Wet bottom basin with narrow emergent zone, mesic prairie slopes, and clusters of hrubs and trees (fall)
Village of Frankfort Stormwater Basin Design Guidelines Page 13
Photo 5 – Ornamental hybrid plantings and water quality enhancement site feature (fall)
Photo 6 – Water quality enhancement features and ornamental hybrid plantings as a component of stormwater management.
Village of Frankfort Stormwater Basin Design Guidelines Page 14
Photo 7 – Wetland bottom basin with mesic prairie slopes and variable width emergent and shoreline plantings (early summer)
Photo 8 – Low profile prairie slopes around a wet bottom basin (early summer)
Village of Frankfort Stormwater Basin Design Guidelines Page 15
Photo 10 – Water quality enhancement cascade with ornamental landscape as part of stormwater management system
Photo 9 – Wet bottom basin with water quality and aesthetic enhancements
Village of Frankfort Stormwater Basin Design Guidelines Page 16
Photo 11 – Cascade and filtration stream with turfgrass and ornamental hybrid landscapingPhoto 12 – Mesic prairie on slopes of wet bottom basin with bicycle path in the background (early summer)
Village of Frankfort Stormwater Basin Design Guidelines Page 17
Photo 13 – Recently installed low-profile prairie and ornamental hybrid combination wetland bottom basin
Photo 14 – Mesic prairie slopes on wet bottom basin (fall)
Village of Frankfort Stormwater Basin Design Guidelines Page 18 Photo 16 – C \\planres1\F\LandA
ascading stream and ornamental hybrid landscaping for water quality and aesthetics
rch\P20161-00 Frankfort Review\Guidelines\Images\Plan Photo Pages.doc